Odanacatib on track for 2013 filing

Odanacatib - currently leading a new class of osteoporosis drugs called cathepsin K inhibitors - has already shown efficacy in reducing fractures in a phase III trial and has been tipped to make sales of $3bn or more at peak.

The latest phase II data indicate that odanacatib significantly increased bone mineral density (BMD) over a two-year period in post-menopausal women with osteoporosis who previously had three or more years of treatment with alendronate, a long-standing drug for the disease which Merck sells as Fosamax.

Patients in the study were randomised to receive either odanacatib or placebo once a week on top of calcium and vitamin D supplements if needed.

At the end of the two-year treatment period, Merck's drug raised BMD by around 1 to 2 per cent - depending on the site tested - while the placebo group saw declines of around the same margin. For example, lumbar spine density increased over 2 per cent with odanacatib but decline by 0.3 per cent in the placebo group.

"We're excited about these results because understanding the effects of odanacatib in a population of post-menopausal women previously treated for osteoporosis is important to clinicians," said Albert Leung, executive director of clinical research at Merck Research Laboratories.

Critically, odanacatib has a favourable safety profile compared to older bisphosphonate-based medicines for osteoporosis like Fosamax, which are associated with gastrointestinal problems as well as rare cases in which bone tissue can start to decay.

Odanacatib is one of five drugs in development at Merck that it hopes will help it return to buoyant growth since losing patent protection on some of its blockbuster brands, notably $6bn-a-year asthma and allergy treatment Singulair (montelukast).